With the development of the wireless multimedia services, people's demands for high data rate and user experience are ever increasing, thereby raising higher requirements on the system capacity and coverage of the traditional cellular network. In a traditional LTE cellular network, a macro base station as a unique network element of the access side provides access services for the UE. Moreover, in order to satisfy the user's demand for the higher data rate and improve the spectral efficiency of the cellular network, a low power node (LPN) is introduced and taken as a supplement to the macro base station in the 3GPP to provide the access services for the UE. The LPN has characteristics such as low costs, low power and easy deployment and so on, and there are normally two kinds of deployment scenarios namely hotspot deployment and enhanced coverage, which can effectively enhance the data rate of high-rate data services in indoor or outdoor hotspot areas, and improve the coverage in remote areas or at cell edges. Generally the LPN also can be called as a small base station, including a home evolved node B (HeNB), a picocell (pico), a remote radio unit/remote radio header (RRU/RRH) and a relay node (RN) and so on. And a cell under the small base station is normally called as a small cell.
In order to make the UE obtain the higher data rate and reduce the power consumption of the UE, it is required that the UE can effectively discover an adjacent small base station node in time, so that a network node can timely shunt the UE to an adjacent small base station to obtain the high data rate, and the load of the macro base station is shunted in the meantime, and small base stations in different geographic areas can multiplex same spectrum resources, to greatly improve the spectral efficiency. On the other hand, the power consumption of the UE is also a problem that the user most concerns. After the UE is shunted to the small base station, it is served by a closer small base station, which can save the power consumption of the UE well. Moreover, a large portion of the power consumption of the UE is also reflected in the discovery and measurement of the adjacent cell. Especially in a case that the small base station and the macro base station use different frequency points, it is required to execute an inter-frequency measurement to complete the cell discovery. In the LTE, the base station is required to configure a measurement gap for the UE when the UE executes the inter-frequency measurement, and the communication between the UE and the serving base station is interrupted to measure an inter-frequency cell during the measurement gap. However, inter-frequency carrier frequencies that can be simultaneously measured by the UE are limited, if the number of different frequencies required to be measured is great, more measurement gaps are configured for the UE, and thus the quantity of electricity required to be consumed when the UE executes the inter-frequency measurement is greater. In addition, in the LTE, with respect to a UE in a connected state, an s-measure mechanism can be adopted to control the UE to start/close measurement behaviors for the adjacent cell, including the inter-frequency measurement. The base station can configure an s-measure value for the UE (namely a serving cell RSRP threshold value), and if the serving cell RSRP value of the UE is greater than a threshold value, it is not required to start the measurement on the adjacent cell.
In the hotspot deployment scenario, in order to achieve the higher data rate and spectral efficiency, it is required to densely deploy a large number of small base stations within the area, and the macro base station and the small base stations may adopt different frequency points, and different frequency points also may be adopted between the small base stations. Particularly, indoor deployment scenarios, such as offices and malls and so on, are normally buildings with many floors, the small base stations may be deployed at all the different floors, and working carrier frequencies of the small base stations of the different floors may be not identical, that is, the UE entering the area is required to execute the inter-frequency measurement with respect to a great number of inter-frequency frequency points in order to discover an adjacent small cell, thereby causing a great amount of power consumption of the UE.
Moreover, in the hotspot deployment scenario, the small base station may be deployed close to the macro base station, that is, it is located in a center area of a cell of the macro base station but is not deployed at the edge of the cell of the macro base station. In the case of adopting the s-measure mechanism, when a UE which a macro cell serves is located within a scope of a small cell in the center area of the macro cell, a serving cell RSRP value obtained through the measurement is still better and is most likely greater than the s-measure value, which causes that the measurement on the adjacent cell cannot be timely triggered and started, and then an adjacent small cell cannot be effectively discovered. The adoption of the related s-measure mechanism is not applicable to the small cell discovery in the hotspot area deployment of the small base station.